This invention relates to a method of manufacture of a drill bit and product resulting therefrom and, more particularly, one that finds advantageous application to oil well drilling.
Contemporary drill bits employ tungsten carbide inserts in steel cone-shaped bodies. The hardness achieved by the tungsten carbide is highly desirable to insure satisfactory life of the drill bits. When it is considered that often these bits are operated many thousands of feet below the surface, anything that extends the life of the bit is desirable because of the extraordinary cost in removal and replacement of the bit. The carbide-equipped cone bits are uniformly manufactured by providing holes in the steel body which are carefully monitored so as to receive and support the carbide inserts. A number of disadvantages flow therefrom in addition to the obvious high cost because of the labor intensive operation. One significant disadvantage is that a substantial amount of carbide must be employed in order to achieve a suitable anchor of the carbide to the supporting bit body. This in turn generates another disadvantage because the amount of space occupied by the carbide limits the space available for the bearings, i.e., the members normally required to permit the cone shaped portions of the bit to rotate during the drilling operation. Thus, in many cases, the life of the bearings determine the life of the bit so that in the past it has been a continuing battle between the carbides and the bearings as to which would outlast the other and therefore prolong the life of the bit itself.
In the past, consideration has been given to the use of integrally cast carbides for the purpose of overcoming certain of the foregoing disadvantages. However, these have been uniformly unsuccessful. Characteristic of integrally cast carbides is the so-called "halo effect" due to any element migration and the development of the eta phase due to carbon starvation. This has been overcome by the instant invention and the provision of an integrally cast drill bit cone constitutes an important objective of the invention.